1. Field of the Invention
This invention relates to polyurethane lacquers containing polyfunctional aromatic nitroso compounds to improve their adhesion to elastomer substrates.
2. Statement of the Related Art
The lacquering of elastomers with polyurethane based lacquers has long been known, cf. G. Klement in "Kautschuk und Gummi-Kunststoffe", Vol. 23 (1970), Number 8, pages 375 to 378. The lacquers described there are used primarily for increasing the weather resistance of relatively sensitive elastomers and for smoothing their surface. Lacquers for elastomers should be used in particular when the elastomer substrate is exposed to prolonged weathering and/or to mechanical stressing. Accordingly, there is a need to provide elastomer lacquers which show better adhesion, even to a polar elastomers. This applies in particular to recently developed low-friction lacquers. These are polyurethane lacquer preparations containing spherical filler particles which are several times thicker than the lacquer film and which act as spacers to reduce the friction of the lacquered elastomer, for example, with respect to glass (see U.S. Pat. No. 4,448,835).
Aromatic nitroso compounds are known per se, as is their use as a component of binders for heat-vulcanizing rubber on metal substrates (see U.S. Pat. No. 3,878,134 and corresponding German Pat. No. 2,228,544). Further, the use of aromatic nitroso compounds in a special adhesive is disclosed in Canadian Pat. No. 1,167,191 and corresponding German patent application No. 31 25 286.